President Bashar al-Assad was fighting to retain control of Syria on Saturday
as the ongoing rebellion in Damascus was followed by a second armed uprising
in the northern city of Aleppo.

While government forces claimed on Saturday to have largely quelled resistance in Damascus, fierce street battles erupted in Aleppo, which is home to three million people and serves as Syria’s main northern commercial hub.

Armed guerrillas from the Free Syrian Army were reported to have entered from the surrounding countryside, bringing fighting for the first time into the downtown area. The city has previously been considered a regime stronghold.

“This night was very bad, there were huge explosions and the gunfire didn’t stop for several hours,” said Mohammad Saeed, an Aleppo-based pro-democracy activist, as hundreds of families fled the city in convoys of cars. “The uprising has finally reached Aleppo.”

The fighting in Aleppo was a sign that the country’s rebel factions are determined to continue pressing home their military initiative after Thursday’s bombing in Damascus, which killed four senior figures in President Assad’s security apparatus.

An alliance between the Alawite Assad family and the predominantly Sunni merchant class in Aleppo is understood to have fractured over recent months, while support for the president has also weakened among powerful local tribal chiefs, whose followers often have access to weapons.

The clashes came as Mr Assad’s forces made some progress in regaining control of the country, targeting border posts siezed by rebels, and dislodging opposition fighters who gained an unprecedented foothold in the Midan district of Damascus on Thursday.

Army helicopters and tanks used rockets, machine guns and mortars to pound rebel fighters in Damascus overnight on Friday, with the city quiet by around 4am GMT, residents told Reuters. Lightly-armed fighters had been moving through the streets on foot and attacking security installations and roadblocks.

“The regime has been rudderless for last three days. But the aerial and ground bombardment on Damascus and its suburbs shows that it has not lost the striking force and that it is re-grouping,” opposition activist Moaz al-Jahhar said by phone from Damascus. Syrian forces later showed reporters the bodies of what they said were rebel fighters lying amidst the rubble.

The Syrian Observatory for Human Rights, a London-based opposition group which monitors the violence in the country, said 240 people had been killed across Syria on Friday, including 43 soldiers. It said the total death toll from the last 48 hours stood at 550, making it the bloodiest two days of the 16-month-old uprising against President Assad.

Many residents in areas of Damascus that were hit by the fighting are taking refuge across the border in neighbouring Lebanon.

“We couldn’t sleep at all, every time we heard firing or the sound of helicopters, we were terrified,” said Abdel Jaber, 45, who passed through the Lebanese border post at Masnaa with his wife and six children yesterday.

Meanwhile, a senior Syrian military defector claimed that Mr Assad’s forces were moving chemical weapons across the country for possible use in a military retaliation for the killing of four top security officials.

“The regime has started moving its chemical stockpile and redistributing it to prepare for its use,” said General Mustafa Sheikh, citing rebel intelligence obtained in recent days.

“They are moving it from warehouses to new locations,” he told Reuters in an interview in southern Turkey, close to the Syrian border. “They want to burn the country. The regime cannot fall without perpetrating a sea of blood.”

US officials say they know the location of at least some of Syria’s chemical weapon stockpile, and have monitored movements of part of the arsenal from storage bunkers to more secure sites earlier this month. It is thought the Assad regime itself shares US anxieties about the stocks falling into the hands of Islamic extremists or Hezbollah. The US is also trying to persuade the Israelis not to invade or bomb Syria in an effort to destroy the stockpiles, which include blister agents and poison gas.

On Saturday evening, Washington said it was “actively consulting” Damascus’s neighbors to stress concerns over the security of all chemical weapons stocks.

“We believe Syria’s chemical weapons stockpile remains under Syrian government control,” said White House spokesman Tommy Vietor. But he added: “Given the escalation of violence in Syria and the regime’s increasing attacks on their people, we remain very concerned about these weapons.”

Separately, a US intelligence source told The Sunday Telegraph that opposition leaders now seemed to backing away from seeking a negotiated settlement with Mr Assad in favour of pursuing outright military victory. That has lead to fears of bloody reprisals against the president’s minority Alawite sect, some of whom are already reported to be fleeing to the Alawite heartlands around the city of Latakia on Syria’s western Mediterranean coast.

However, Washington does not believe Mr Assad’s fall is imminent, the source said, predicting that he would cling to power for another two or three months.

In other developments, Syrian army units shelled rebels who siezed control of one of three main crossings between Iraq and Syria, Iraqi officials said. The officials also said that Syrian refugees had attempted to enter Iraq but that Baghdad had ordered its security forces to refuse them access.

Mr Sheikh claimed that momentum gained by the rebels was now prompting ever more defections, and that at least 100,000 soldiers had deserted out of the 320,000-strong military, almost double the numbers of only a few months ago. On Saturday a Turkish official said that two Syrian brigadier-generals had also fled to Turkey overnight.

Opposition sources claim that the government has now deployed elite forces from the Fourth Brigade and the Republican Army against the rebels, indicating that they are using every last weapon at their disposal.

Speaking on a visit to Croatia, Ban Ki-moon, the United Nations secretary general, said that Syrian authorities had “manifestly failed” to protect civilians and called on the international community to act to stop the violence.

Mr Ban also called on both government and opposition forces alike “to stop armed violence without any conditions”.